Papers by Aristea I . Ladas
Prospective Memory, Sustained Attention and Response Inhibition in Poly-Substance Users Stable on Methadone Maintenance Treatment
Substance Use & Misuse
Towards a hybrid approach to unveil the Chimaira of neurosciences: philosophy, aperiodic activity and the neural correlates of consciousness
Frontiers in Human Neuroscience
Contemporary theories of consciousness, although very efficient in postulating testable hypothese... more Contemporary theories of consciousness, although very efficient in postulating testable hypotheses, seem to either neglect its relational aspect or to have a profound difficulty in operationalizing this aspect in a measurable manner. We further argue that the analysis of periodic brain activity is inadequate to reveal consciousness’s subjective facet. This creates an important epistemic gap in the quest for the neural correlates of consciousness. We suggest a possible solution to bridge this gap, by analysing aperiodic brain activity. We further argue for the imperative need to inform neuroscientific theories of consciousness with relevant philosophical endeavours, in an effort to define, and therefore operationalise, consciousness thoroughly.
Front. Hum. Neurosci., Sec. Cognitive Neuroscience, 2023
Contemporary theories of consciousness, although very efficient in postulating testable hypothese... more Contemporary theories of consciousness, although very efficient in postulating testable hypotheses, seem to either neglect its relational aspect or to have a profound difficulty in operationalizing this aspect in a measurable manner. We further argue that the analysis of periodic brain activity is inadequate to reveal consciousness's subjective facet. This creates an important epistemic gap in the quest for the neural correlates of consciousness. We suggest a possible solution to bridge this gap, by analysing aperiodic brain activity. We further argue for the imperative need to inform neuroscientific theories of consciousness with relevant philosophical endeavours, in an effort to define, and therefore operationalise, consciousness thoroughly.
Arterial Stiffness Alterations in Simulated Microgravity and Reactive Sledge as a Countermeasure
High Blood Pressure & Cardiovascular Prevention, 2021
Introduction Experiments during spaceflight and simulated microgravity as head-down tilt bedrest,... more Introduction Experiments during spaceflight and simulated microgravity as head-down tilt bedrest, demonstrated the role of arterial stiffness among others, in microgravity induced cardiovascular pathologies and emphasized the need for a robust countermeasure. Aim The purpose of the present study was to evaluate the use of a new countermeasure, consisting of a high intensity Reactive Sledge (RSL) jumps training protocol, to counteract changes in arterial stiffness during long term head down tilt bedrest (LTBR). Methods The participants enrolled in the study were 23 male, healthy volunteers, aged between 20 and 45 years, subjected to LTBR for 60 days and randomly assigned either to a control (11) or to a training sledge (12) group using RSL 3–4 times per week, as a countermeasure. Recorded values were systolic and diastolic blood pressure, heart rate and the user’s arterial stiffness index. Results Compared to baseline measurements, there was a deterioration in the values of arterial stiffness, systolic and diastolic blood pressure and heart rate, in both groups until day 35 of LTBR, interpreted as adaptation to the microgravity environment. From this day until the end of the experiment, arterial stiffness of the control group was constantly fluctuating, while constantly improving for the training group. During the recovery period, arterial stiffness values returned to the pre-experimental levels in both groups. Conclusions Overall, arterial stiffness increased the longer the time spent in LTBR and the countermeasure was partially effective in preventing the observed phenomenon. German Clinical Trials Register (DRKS), DRKS00012946, September 18, 2017, retrospectively registered
Neuroscience Letters, 2011
Subjects were assessed before and after the intervention with a neuropsychological battery includ... more Subjects were assessed before and after the intervention with a neuropsychological battery including, among other tests, the California Verbal Learning Test (CVLT), the Trail Making Test A and B (TMT-A, TMT-B) and the Digit Span forward and backwards. Results: A mixed between-within subjects' analysis of variance, with gender as the between-subjects factor, revealed a significant main effect of the intervention program (pre-intervention/postintervention) on three neuropsychological measures. Significant improvement was observed on the TMT-B completion time (Wilks Lambda = 0.730, F(1,17) = 6.300, p = 0.022), the CVLT recognition performance (Wilks Lambda = 0.749, F(1,17) = 5.682, p = 0.029), and the number of repetitions while performing the CVLT (Wilks Lambda = 0.700, F(1,17) = 7.276, p = 0.015). No significant effect of the intervention program was observed for the digit span score, both for the forward and the backward conditions. Conclusions: The present findings suggest that the application of a combined CT and PT intervention program may have a positive impact on the executive and verbal memory functions in the elderly population.
The SEE-VIEW Working Papers Series was launched in 2017 with the purpose of disseminating researc... more The SEE-VIEW Working Papers Series was launched in 2017 with the purpose of disseminating research and policy debate on subjects related to interdisciplinary issues in the Social Sciences and beyond, focusing on the region of SouthEast Europe. The working papers published in the Series constitute work in progress circulated to stimulate discussion and critical comments.
There is growing evidence that brain structure and cognitive performance can be moulded from vari... more There is growing evidence that brain structure and cognitive performance can be moulded from various forms of experience. Bilingualism seems to form such an experience, with studies mainly showing a bilingual advantage over monolinguals in executive control of attention. This has been attributed to bilinguals’ lifelong practice in controlling two simultaneously active languages while using only one during communication. However, the problematic replicability of some of the main findings of relevant studies suggests that a confounding factor may have influenced their results. We suggest this could be the socioeconomic status (SES) of the participants, which has been inadequately controlled for in the majority of those studies, despite evidence on SES’s strong influences on the cognitive system. Also, research has largely neglected the possible effects of bilingualism in the other two main attention functions, alerting and orienting. Four experiments were designed to explore the bilin...
Neuroscience Letters, 2011
The moderating effect of bilingualism on lifespan cognitive development
Cognitive Development
Revisiting the bilingual advantage in attention in low SES Greek-Albanians: does the level of bilingual experience matter?
Language, Cognition and Neuroscience
Frontiers in Aging Neuroscience
In the present study we investigated the efficacy of the differential outcomes procedure (DOP) to... more In the present study we investigated the efficacy of the differential outcomes procedure (DOP) to improve visuospatial working memory in patients with Alzheimer's disease and mild cognitive impairment (MCI). The DOP associates correct responses to the to-beremember stimulus with unique outcomes. Eleven patients diagnosed with Alzheimer's disease, 11 participants with MCI, and 17 healthy matched controls performed a spatial delayed memory task under the DOP and a control condition (non-differential outcomes-NOP-). We found that performance (terminal accuracy) was significantly better in the DOP condition relative to the NOP condition in all three groups of participants. AD patients performed worse, and took longer to benefit from the DOP. In line with previous animal and human research, we propose that the DOP activates brain structures and cognitive mechanisms that are less affected by healthy and pathological aging, optimizing in this way the function of the cognitive system.
Frontiers in Aging Neuroscience
In the present study we investigated the efficacy of the differential outcomes procedure (DOP) to... more In the present study we investigated the efficacy of the differential outcomes procedure (DOP) to improve visuospatial working memory in patients with Alzheimer's disease and mild cognitive impairment (MCI). The DOP associates correct responses to the to-beremember stimulus with unique outcomes. Eleven patients diagnosed with Alzheimer's disease, 11 participants with MCI, and 17 healthy matched controls performed a spatial delayed memory task under the DOP and a control condition (non-differential outcomes-NOP-). We found that performance (terminal accuracy) was significantly better in the DOP condition relative to the NOP condition in all three groups of participants. AD patients performed worse, and took longer to benefit from the DOP. In line with previous animal and human research, we propose that the DOP activates brain structures and cognitive mechanisms that are less affected by healthy and pathological aging, optimizing in this way the function of the cognitive system.
Recently, a transitional stage, called Mild Cognitive Impairment (MCI) has
been identifie... more Recently, a transitional stage, called Mild Cognitive Impairment (MCI) has
been identified. Early MCI detection is of crucial importance for preventing dementia
onset. The aim of this study is to provide a classification framework able to
discriminate subtle alterations due to neurodegenerative processes. Primary attention
was given at the MCI stage. Therefore two MCI groups were formed according the
patient’s performance in the Montreal Cognitive Assessment (MoCA) test; a group of
39 patient with a low cognitive decline (MCI-1; MoCA>=25), and a group of 31
patients with moderate cognitive decline group (MCI-2; MoCA <25. In addition, we
tested 17 healthy control participants, and 14 mild demented patients. Participants
underwent a full neuropsychologic examination.
Application of the Independent Component Analysis (ICA) and visual
inspection of EEG data during resting state condition with eyes closed was initially
adopted for noise rejection. Then, the energy for each frequency band was computed
through discrete wavelet transform (DWT). These spectral components for 57
electrodes served as an input to a classification system employing Mahalanobis
Distace. Classification results (84.16% overall accuracy) demonstrated the system’s
robustness and reliability. Discrimination reached 82.35% for healthy controls,
92.31% for MCI-1, 74.19% for MCI-2 and 85.71% for mild demented patients. The
classification system is proposed in order to supplement the neuropsychologic
examination and to correlate subtle cognitive deficits revealed by MoCA with
modified neurophysiological patterns, providing thus a better understanding to the
progression of neurodegenerative mechanisms.
In the present study we investigated the efficacy of the differential outcomes procedure (DOP) to... more In the present study we investigated the efficacy of the differential outcomes procedure (DOP) to improve visuospatial working memory in patients with Alzheimer's disease and mild cognitive impairment (MCI). The DOP associates correct responses to the to-beremember stimulus with unique outcomes. Eleven patients diagnosed with Alzheimer's disease, 11 participants with MCI, and 17 healthy matched controls performed a spatial delayed memory task under the DOP and a control condition (non-differential outcomes -NOP-). We found that performance (terminal accuracy) was significantly better in the DOP condition relative to the NOP condition in all three groups of participants. AD patients performed worse, and took longer to benefit from the DOP. In line with previous animal and human research, we propose that the DOP activates brain structures and cognitive mechanisms that are less affected by healthy and pathological aging, optimizing in this way the function of the cognitive system.
Detection of emotional content in the elderly using neurophysiological recordings
Attentional processes of children bilingual in Albanian and Greek
Research has shown that bilingual adults outperform monolinguals in tasks of cognitive control. T... more Research has shown that bilingual adults outperform monolinguals in tasks of cognitive control. This bilingual proficiency has been attributed to the lifelong training bilinguals undergo to manage two linguistic systems (e.g. Bialystok et al., 2005; Bialystok & De Pape, 2009; Bialystok & Martin, 2004; Colzato et al., 2008; Costa, Hernández & Sebastian-Galles, 2008). However, most of the studies conducted so far suffered from several methodological limitations, the most important of which being the lack of control for Socio-Economic Status (SES) of the participants, a factor repeatedly shown to influence cognitive performance (e.g. Mezzacappa, 2004; Siegal, Surian, Matsuo, Geraci, Iozzi, Okumura et al., 2010). Moreover, while executive attention has been relatively well studied, the two other functions of attention, alertness and visuospatial orienting, have been largely ignored in studies of bilingualism. Hence, our first aim was to study the influence of bilingualism on the three m...
The relationship between dopamine activity and cognitive function in Mild Cognitive Impairment: Eye Blink Rate as a reliable measure of brain dopamine activity
Objective : We investigated the relationship between dopamine (DA) activity, as measured by Eye B... more Objective : We investigated the relationship between dopamine (DA) activity, as measured by Eye Blink Rate (EBR), and cognitive function in old adults with Mild Cognitive Impairment (MCI). Research is not conclusive about the factors responsible for the transition from MCI to dementia. However, studies suggest that cortical hyperexcitability in very early stages of pathological aging, may progressively lead to cell death, and thus to Alzheimer’s disease. Consequently, we speculated that abnormally increased dopamine activity may characterize people with MCI, and account for their poor cognitive function. Participants and Methods: Thirty three healthy old adults, and 36 old adults with MCI (Mean age= 67.3 y.o, ± 7.13) participated in the study. The EBR , a reliable measure of brain DA function, was recorded for 6 minutes under resting conditions, using two gold skin electrodes placed above and below the left eye. Cognitive function was assessed with a battery of neuropsychological te...
Using synchronization techniques based on wavelet entropy for the early diagnosis of Alzheimer's with electroencephalogram
Attentional mechanisms in bilingualism
It has often been reported that bilinguals outperform monolinguals on tests of cognitive control.... more It has often been reported that bilinguals outperform monolinguals on tests of cognitive control. However, most of the studies conducted so far suffered from several limitations. For example, bilinguals and monolinguals have not been well matched on non-linguistic measures such as socio-economic status that could provide an alternative interpretation of bilingual advantages. Moreover, while executive attention has been relatively well studied in bilingualism, two other functions of attention, alertness and visuospatial orienting, have been largely neglected. Hence, we studied the influence of bilingualism on the three main attentional networks: alerting, orienting and executive control of attention, taking SES into account. We used the computerized Attentional Networks Task (ANT; Fan et al., 2002) to measure attention processes of bilinguals and control groups of monolinguals, a computerized Joint Attention task, similar to that of Frischen and Tipper (2004), to investigate the orie...
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Papers by Aristea I . Ladas
been identified. Early MCI detection is of crucial importance for preventing dementia
onset. The aim of this study is to provide a classification framework able to
discriminate subtle alterations due to neurodegenerative processes. Primary attention
was given at the MCI stage. Therefore two MCI groups were formed according the
patient’s performance in the Montreal Cognitive Assessment (MoCA) test; a group of
39 patient with a low cognitive decline (MCI-1; MoCA>=25), and a group of 31
patients with moderate cognitive decline group (MCI-2; MoCA <25. In addition, we
tested 17 healthy control participants, and 14 mild demented patients. Participants
underwent a full neuropsychologic examination.
Application of the Independent Component Analysis (ICA) and visual
inspection of EEG data during resting state condition with eyes closed was initially
adopted for noise rejection. Then, the energy for each frequency band was computed
through discrete wavelet transform (DWT). These spectral components for 57
electrodes served as an input to a classification system employing Mahalanobis
Distace. Classification results (84.16% overall accuracy) demonstrated the system’s
robustness and reliability. Discrimination reached 82.35% for healthy controls,
92.31% for MCI-1, 74.19% for MCI-2 and 85.71% for mild demented patients. The
classification system is proposed in order to supplement the neuropsychologic
examination and to correlate subtle cognitive deficits revealed by MoCA with
modified neurophysiological patterns, providing thus a better understanding to the
progression of neurodegenerative mechanisms.